The numerical analysis using a high-speed computer is performed in various fields. For example, in a medical field, the numerical analysis to reproduce the phenomena of the heart is conducted for a coronary circulation (a coronary artery and coronary vein) that is an organ for transporting oxygen and the like to the heart. In this numerical analysis, there is a case where a model using the collinear approximation, in other words, a model in which plural segments are connected, instead of using the tubular shape for the vessel as it is.
A tubular object visualization program to visualize such a model in which the plural segments are connected as a tubular object has already exist, however, a problem as illustrated in FIG. 1 occurs, when this visualization program is used as it is. In an example of FIG. 1, two segments are connected at one point, however, when the two segments are not on one straight line, a first tubular object Y that is generated for a first segment and a second tubular object Z that is generated for a second segment are not appropriately jointed, and a gap X occurs. Such a gap does not exist in the actual vessel, however, the existing visualization program does not have any means to solve such a problem.